Mast cell activation by NGF drives the formation of trauma-induced heterotopic ossification
Tao Jiang, Xiang Ao, Xin Xiang, Jie Zhang, Jieyi Cai, Jiaming Fu, Wensheng Zhang, Zhenyu Zheng, Jun Chu, Minjun Huang, Zhongmin Zhang, Liang Wang
Tao Jiang, Xiang Ao, Xin Xiang, Jie Zhang, Jieyi Cai, Jiaming Fu, Wensheng Zhang, Zhenyu Zheng, Jun Chu, Minjun Huang, Zhongmin Zhang, Liang Wang
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Research Article Bone biology Immunology

Mast cell activation by NGF drives the formation of trauma-induced heterotopic ossification

Abstract

Soft tissue trauma can cause immune system disturbance and neuropathological invasion, resulting in heterotopic ossification (HO) due to aberrant chondrogenic differentiation of mesenchymal stem cells (MSCs). However, the molecular mechanisms behind the interaction between the immune and nervous systems in promoting HO pathogenesis are unclear. In this study, we found that mast cell–specific deletion attenuated localized tissue inflammation, with marked inhibition of HO endochondral osteogenesis. Likewise, blockage of nerve growth factor (NGF) receptor, known as tropomyosin receptor kinase A (TrkA), led to similar attenuations in tissue inflammation and HO. Moreover, while NGF/TrkA signaling did not directly affect MSCs chondrogenic differentiation, it modulated mast cell activation in traumatic soft tissue. Mechanistically, lipid A in LPS binding to TrkA enhanced NGF-induced TrkA phosphorylation, synergistically stimulating mast cells to release neurotrophin-3 (NT3), thereby promoting MSC chondrogenic differentiation in situ. Finally, analysis of single-cell datasets and human pathological specimens confirmed the important role of mast cell–mediated neuroinflammation in HO pathogenesis. In conclusion, NGF regulates mast cells in soft tissue trauma and drives HO progression via paracrine NT3. Targeted early inhibition of mast cells holds substantial promise for treating traumatic HO.

Authors

Tao Jiang, Xiang Ao, Xin Xiang, Jie Zhang, Jieyi Cai, Jiaming Fu, Wensheng Zhang, Zhenyu Zheng, Jun Chu, Minjun Huang, Zhongmin Zhang, Liang Wang

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Figure 9

scRNA-Seq analysis and human traumatic tissue assay confirm the involvement of NGF/TrkA signaling and mast cell–derived NT3 in HO.

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scRNA-Seq analysis and human traumatic tissue assay confirm the involvem...
(A) Schematic diagram of the experimental workflow for the scRNA-Seq dataset GSE126060. (B) UMAP plots revealed 12 distinct cell clusters, including mast cells (red dashed line). (C) Bubble plot showing the expression of Ntf3 and Ntrk1 in 5 types of immune cells. (D) Seven days after HO induction, mast cells exhibited a high expression level of Ntf3 and Ntrk1 (red box). (E, F, K, and L) Representative H&E (E), TB staining images (F), and quantification of the total cells (K) and mast cells (L) count in human tendons at 0 and 7 days after trauma, as well as in HO tissues. Black arrows indicate inflammatory cell and mast cell. Scale bar: 5 μm. n = 4 biological replicates. (G, H, M, and N) Representative IHC staining images (G and H) and quantification of NGF, TrkA, and TrkC expression (M and N) in human ligaments at 0 and 7 days after trauma, as well as in HO tissues. Black arrows indicate positive areas. Scale bar: 5 μm. n = 4 biological replicates. (I, J, and O) Representative polychromatic immunofluorescence staining images (I and J) and quantification of TrkC+/TrkA+ (green), CAM1+ (red), and NT3+ (silver) cells (O) in human ligaments at 7 days after trauma, with DAPI counterstaining (blue). The number of colocalized positive cells was counted. Yellow arrows indicate mast cells. Scale bar: 80 μm (left) and 20 μm (right). n = 4 biological replicates. Data are representative of 2 independent experiments (E–O). Data were shown as mean ± SD and compared with 1-way ANOVA with Tukey’s multiple-comparison test (K–M) or 2-tailed unpaired Student’s t test (N and O).